The present invention relates to water treatment, and in particular to a method and apparatus for remediating wastewater holding areas and the like.
There have been developed over the years many different systems and devices for remediating wastewater holding areas, such as lagoons, ponds, holding vessels, basins, and other similar structures. Because of ecological considerations, research and development for feasible and economical solutions for cleaning up or remediating wastewater and other types of contaminated water have been greatly accelerated.
The modern treatment of domestic wastewater through biological means results in a residual byproduct comprised mostly of bacterial cell material and inert debris. A common practice in the treatment of domestic wastewater is to utilize large holding vessels, also known as lagoons, to provide the necessary detention time and environmental conditions to complete the treatment process. Clear liquid effluent is decanted from the treatment zone on a periodic basis, thereby leaving solid residuals as a settled sludge in the lower portion of the lagoon. Over time, the sludge accumulates, necessitating periodic removal. The sludge, which typically settles at the bottom of the lagoon, does not normally behave as a fluid, but rather resembles a heavy viscous or soft gelatinous material. It has been found that when a conventional pump is used to remove sludge from a retention area, the pump normally removes only a small area or portion of the sludge, such that complete remediation of the lagoon is difficult due to the unique characteristics of the sludge.
A number of different approaches have been utilized in the prior art for remediating wastewater holding areas and/or dewatering sludge. One such method comprises removing the surface water from the lagoon and dewatering the sludge through evaporation on an open drying bed prior to removal to a dumpsite. However, such processes are relatively invasive, and not environmentally sensitive to the adjacent area. Furthermore, the remediation process removes the lagoon from service, and undesirable odors often result from the long drying process, which typically requires turning over the sludge to achieve additional drying. Such methods also are not particularly effective in thoroughly drying the sludge to achieve a minimum volume, so as to facilitate removal and deposit of the dewatered sludge.
Other prior art dewatering sludge processes include utilizing belt presses, filter presses, centrifuges and sludge drying beds. The various sludge press and centrifuge systems are expensive to purchase, operate and maintain.
Consequently, a need exists for a cost effective, environmentally sensitive technique to remediate wastewater holding areas and the like in a non-intrusive manner, while keeping the lagoon in service.
One aspect of the present invention is a method for remediating wastewater holding areas and the like of the type having a bottom with sludge deposited thereon, and water over the sludge which defines an upper surface of an associated lagoon. The method includes forming a closed foraminous dewatering membrane configured to dewater sludge slurry therein. The dewatering membrane is positioned adjacent to the wastewater holding area at an elevation above the elevation of the upper surface of the lagoon. Sludge and adjacent water from the bottom of the lagoon are pumped in the form of a sludge slurry into the interior of the dewatering membrane. Water is removed from the sludge slurry by allowing gravitational forces to flow water through the dewatering membrane back into the lagoon. The dewatering membrane is then opened, and the dewatered sludge is removed for deposit at an appropriate site.
Another aspect of the present invention is a method for removing sludge from water holding areas and the like, comprising the steps of forming a closed foraminous watering membrane configured to dewater a sludge slurry therein. The dewatering membrane is positioned adjacent to a water holding area. Sludge and adjacent water from the bottom of the water holding area are pumped in the form of a sludge slurry into the interior of the dewatering membrane. The water is removed from the sludge slurry by allowing gravitational forces to flow water through the dewatering membrane. The dewatering membrane is then opened, and the dewatered sludge removed for deposit at an appropriate site.
Yet another aspect of the present invention is an apparatus for removing sludge from wastewater holding areas and the like, comprising a cutter head adapted to be positioned adjacent to the bottom of a wastewater holding area and configured to draw therethrough sludge and adjacent water in the form of a sludge slurry. The apparatus also includes a dewatering membrane having a closed interior with a foraminous construction adapted to dewater sludge slurry deposited therein. A pump is operably connected with the cutter head and the dewatering membrane, whereby sludge slurry is drawn from the bottom of the wastewater holding area and is transported into the interior of the dewatering membrane, whereby gravitational forces flow water in the sludge slurry through the dewatering membrane to create a dewatered sludge which can be transported in generally solid form to an appropriate site.
The present invention provides a cost effective, timesaving and environmentally sensitive method and apparatus for treating water, including removing sludge from wastewater holding areas and the like. The present method and apparatus permit the water holding area to be treated, without removing the same from service, thereby resulting in substantial cost savings. Minimum impact to the surrounding environments, reduced odor, and improved drying to minimize dewatered sludge removal are also aspects of the present invention.
These and other advantages of the invention will be further understood and appreciated by those skilled in the art by reference to the following written specification, claims and appended drawings.